Classifier for fine solids

ABSTRACT

A modification of apparatus for separating fine particles from a gaseous fluid secondary provide means for classifying the fine particles is presented. The apparatus for separating particles from fluid is like that disclosed and claimed in U.S. Pat. No. 3,199,268 granted Aug. 10, 1965 to Karl-Heinz Oehlrich et al. This prior invention involves a primary flow of particles entrained in a fluid medium generally axially of a cylindrical processing chamber from an inlet duct near one end to an outlet duct at the other axis. A solid ground closes a portion of the chamber near the inlet duct save for an annular open space next to the wall of the chamber. A wecondary circulatory flow is imparted to the fluid medium above the solid ground which causes the solid particles to be separated from the medium and to fall through the annular space into a collecting hopper. The modification provides a fluid inlet to the hopper to cause a stream of controlled velocity to pass upwardly through the annular space counter current to the falling stream of particles so as to drive particles of a predetermined size to be classified from the rest of the particles and to be carried through the outlet duct.

[H1 3,720,314 l iMarch '13, 1973 CLASSIFIER FOR FINE SOLIDS Hohn F.Phillippi, Cleveland, Ohio [73] Assignee: Aerodyne DevelopmentCorporation,

Cleveland, Ohio [22 Filed: Nov. 9, 1970 21 Appl. No.: 87,993

[75] Inventor:

OTHER PUBLICATIONS German printed application 1,407,989, dated 1-70,Siemens. v

Aerodyne Development Article-Aerodyne Development Corp., Ohio,-pagesl2,'dated I0-68.

Primary Examiner-Bernard Nozick Attorney-Baldwin, Egan, Walling & Fetzer57 ABSTRACT A modification of apparatus for separating fine particlesfrom a gaseous fluid secondary provide means for classifying the fineparticles is presented. The ap paratus for separating particles fromfluid is like that disclosed and claimed in U.S. Pat. No. 3,199,268granted Aug. 10, 1965 to Karl-Heinz Oehlrich et al. This prior inventioninvolves a primary flow of particles entrained in a fluid mediumgenerally axially of a cylindrical processing chamber from an inlet ductnear one end to an outlet duct at the other axis. A solid ground closesa portion of the chamber near the inlet duct save for an annular openspace next to the wall of the chamber. A wecondary circulatory flow isimparted to the l'luid m edium above the solid ground which causes thesolid particles to be separated from the medium and to fall through theannular space into a collecting hopper. The modification provides afluid inlet to the hopper to cause a stream of controlled velocity topass upwardly through the annular space counter current to the fallingstream of particles so'as to drive particles of a predetermined size to,be clas-v sified from the rest of the particles and to be carried,

through the outlet duct.

9 Claims, 2 Drawing Figures CLASSIFIER FOR FINE SOLIDS An object of thepresent invention is to provide an apparatus for the classification offinely divided solids by the modification of a previously knownapparatus for separating fine particles from a fluid medium. This priordevice is illustrated in U.S. Pat. No. 3,199,268, granted Aug. 10, 1965to Karl-Heinz Oehlrich et al. for Particle-from-gas Separators. Thisprior patented device passes a fluid medium containing finely dividedparticles of different sizes through a generally cylindrit calprocessing chamber from an inlet duct to an outlet duct. This priorpatented structure provides a circulatory flow along the walls of theprocessing chamber toward the inlet end thereof, preferably by theintroduction of one or more jets of a second medium supply introducedtangentially of the walls of the processing chamber and inclineddownwardly toward the inlet end of the processing chamber. On the inletduct, there is provided a solid ground which extends radially outwardlyfrom the duct to a zone spaced from the walls of the processing chamberand leaving an open annular passageway at that point. The particlesseparated from the fluid medium fall downwardly through this openannular space into a receiving hopper beneath. The present inventionintroduces into this hopper an additional fluid stream for classifyingpurposes under a velocity so controlled as to entrain falling particlesof a predetermined size at the open annular space, driving theseparticles, of predetermined size only, counter current to the heavierparticles so as to carry only the classified particles through theoutlet duct. 1

I Other objects and advantages of the present invention will be apparentfrom the accompanying drawings and description and the essentialfeatures thereof will be set forth in the appended claims.

In the drawings,

FIG. 1 is a central sectional view through apparatus involving thisinvention; while FIG. 2 is a sectional view similar to the lower portionof FIG. 1 and includingsome stationary vanes in the processing chamberupstream from the solid ground so constructed and arranged as to directthe classifying fluid medium outwardly toward the side walls of theprocessing chamber.

To fully understand the basic apparatus which is modified by the presentinvention, reference may be had to U.S. Pat. No. 3,199,268, granted Aug.10, 1965 to Karl-Heinz Oehlrich et al. which is incorporated herein byreference. It will be sufficient to state here that this prior patentincludes a processing chamber having rotationally symmetrical sidewalls, such as a cylindrical form which is represented herein in thedrawings, although approximately cylindrical forms would be rotationallysymmetrical also. While this apparatus is shown herein as standing in avertical position, it should be understood that the same apparatus maybe positioned horizontally or otherwise as desired. Near the lower endof the processing chamber 11 there is fixed an inlet duct 12 for theintroduction of a gaseous medium containing finely divided particles ofvarying sizes. At the upper end of the processing chamber is an outletduct 13 which is either substantially coaxial with, or on a parallelaxis with, the upper end of the inlet duct 12. The flow between the duct12 and the duct 13 is herein referred to as a primary flow along an axispassing through the ducts 12 and 13. Agitating means is provided forimparting to the primary flow a circulatory secondary flow causing thesolid particles in the primary flow to move toward the cylindrical sidewalls 10. One such means comprises stationary vanes 14 fixed at thedischarge end of the inlet duct, all of these vanes inclined upwardlyand outwardly and in the same clock direction.

A second such agitating means comprises a plurality of jet openings 15in communication with a manifold 16 into which a second gaseous mediumis introduced at 17. The jet openings 15 introduce gaseous jets at ahigher energy level than the primary flow in the processing chamber 1 1tangentially of the walls 10 and inclined downwardly toward the inletend of the processing chamber. In the drawing of FIG. 1, the primaryflow is represented by the dash-dot-dot-dash lines, while the secondaryflow is represented by the dash-dot-dash lines.

A solid ground is provided at 118 which consists of a fin extendingradially outwardly from the inlet duct 12 to a zone short of the sidewalls 10 leaving there an open annular space 19.

As explained in the previously mentioned patent, the construction issuch that the finely divided solid particles move on the periphery nearthe side walls 10 on a helical line downwardly in the processing chamberbut, when they reach the solid ground 18, the motion converts to anapproximately logarithmic spiral along which the particles reach thecenter of the processing chamber whence they rise in a vortex filamentnear the primary flow axis. At a certain height, inversely proportionalto the square root of the angular velocity, a spatial vortex sourceforms itself. There, the particles are flung outwardly until they reachthe downwardly directed agitating circulatory secondary flow caused bythe jets 15.

To carry out the classifying step of the present invention, a gaseousstream for classifying purposes is introduced at the duct 20 which leadsinto the solid particle collection chamber 11a which consists of thatportion of the processing chamber below the solid ground 18. Means mustbe provided for controlling the velocity of the gaseous stream provided.in duct 20. Such a means is represented by the valve 21 in the duct 20,although those skilled in this art will understand that wheresubstantially constant conditions occur over a period of time, thecontrol means might be the original selection of the size of the duct 20itself. The duct 20 may be directed radially inwardly of the processingchamber or tangentially thereof. The flow of the classifying gaseousmedium is indicated by the dotted lines of FIGS. 1 and 2. As theclassifying medium reachesthe open annular space 19 radially outside ofthe solid ground 18, it engages the stream of solid particles flowingdownwardly through this same space 19 in a counter current effect, theresult of which is that particles of a predetermined size only arecarried upwardly through the space 19 counter current to the heavierparticles coming downwardly through this space. Such classifiedparticles of predetermined size are carried upwardly through the chamber11 and outwardly through the outlet duct 13.

As shown in FIG. 2, means may be provided if necessary or desirable toprovide an even distribution of the flow of the classifying mediumtoward the open annular space 19. This is shown as a plurality ofturning vanes 22 rigidly secured to the inlet duct 12 as by providingtwo semi-circular subassemblies which may be clamped around the inletduct 12in a well known manner. These vanes 22 are inclined upwardly andoutwardly and all in the same clock direction so as to insure evendistribution of the stream entering at duct 20 circumferentially aroundall portions of the annular space 19.

Either or both of the agitating means 14 and 15 may be utilized as abovedescribed. Use of the agitating spinner 14 requires less power needed atthe jets 15.

One of the uses of the classifier of this invention would be inconnection with a grinding operation where the discharge from thegrinder is fed into the inlet duct 12 so as to classify and separatethrough the outlet duct 13 a predetermined size of fines while returningto the grinder the larger particles collected in the hopper 1 1a, suchas by a discharge valve connected in place of the closure plate 23 atthe bottom of the processing chamber.

Another use of this invention would be to collect all of the finelydivided solid particles discharging from a rotary cement kiln andpassing them through the inlet duct 12 of the present apparatus. Suchfine particles, for instance, might run from 100 microns down to closeto zero, of which a range of approximately microns and down are stronglyalkaline which would ruin the cement product. In the use of the presentinvention, the classifying gaseous medium entering through the duct 20is so controlled that these very fine particles of 20 microns andsmaller are carried upwardly through the annular space 19 and outthrough the outlet duct 13 where they are discharged to a suitablepoint. The heavier particles from 100 microns to about 20 microns wouldbe collected in the hopper 11a and carried by any suitable meansattached in place of plate 23 back to the inlet end of the cement kiln.In one such use of this invention, the classification of the very fineparticles from 20 microns and down was about 99 percent efficient,whereas the separation of the heavier particles from 100 microns toabout 20 microns was also about 99 percent efficient.

While this invention has been described using a gaseous medium, itshould be understood that it may also use a liquid medium.

What is claimed is:

1. In apparatus for separating solid particles entrained in a fluidmedia, comprising an elongated processing chamber having approximatelycylindrical side walls and having an inlet duct near one end for theintroduction of solid particles of varying sizes entrained in a fluidmedium and means for swirling the fluid media from said inlet duct, saidchamber having an outlet duct near its other end, said two ducts beingsubstantially coaxial and defining together a primary flow axis alongwhich said fluid medium travels from said inlet duct to said outletduct, agitating means for imparting to the primary flow of the medium insaid chamber a circulatory secondary flow causing said solid particlesto move through said chamber toward said inlet and adjacent said sidewalls, means forming a solid ground near the terminal end of said inletduct extending radially outwardly therefrom and terminating short ofsaid side walls and leaving there an annular open space through whichpass said solid particles moving toward said inlet end adjacent saidside walls, means providing a collection chamber for said solidparticles upstream of said inlet end beyond said solid ground, thearrangement being such as to form in said processing chamber a vortexsink near said solid ground and a vortex source remote from said inletduct toward said outlet duct; the combination therewith of means forclassifying as to size said solid particles passing through said openspace, comprising means for introducing into said processing chamber atthe inlet end thereof upstream of said primary flow from said solidground a fluid stream for classifying purposes, means for substantiallyeven dispersing said fluid stream about said annular space and directingthe fluid stream downstream through said space towards the outlet ducttogether with means for controlling the velocity of said classifyingstream, said side walls and said inlet and said solid ground confiningsaid classifying stream to said annular open space, whereby particles ofpredetermined smaller size only are driven counter current from saidsolid particles passing through said annular open space and the same arecarried through said processing chamber and through said outlet duct.

2. Apparatus as defined in claim 1, wherein said processing chamber issubstantially vertical with said outlet duct uppermost.

3. Apparatus as defined in claim 1, wherein said agitating meanscomprises stationary vane means where said inlet discharges into saidprocessing chamber so constructed and arranged as to impart acirculatory motion to the fluid medium discharged there.

4. Apparatus as defined in claim 1, wherein said fluid stream forclassifying purposes is directed substantially radially with respect tosaid processing chamber.

5. Apparatus as defined in claim 1, wherein said fluid stream forclassifying purposes is directed substantially tangentially with respectto said processing chamber.

6. Apparatus as defined in claim 1, including vane means in saidprocessing chamber upstream from said solid ground so constructed andarranged as to direct said classifying fluid medium outwardly towardsaid side walls of said processing chamber.

7. Apparatus as defined in claim I, wherein said solid particlesintroduced at said inlet duct are entrained in a gaseous medium, andsaid fluid stream for classifying purposes is gaseous.

8. Apparatus as defined in claim 1, wherein said agitating meanscomprises a plurality of fluid-injection nozzle means circumferentiallyspaced from each other about said axis, said nozzle means also beingaxially spaced from each other along said processing chamber, each ofsaid nozzle means being directed substantially tangentially to said sidewalls and inclined toward said inlet end.

9. Apparatus as defined in claim 8, including a stationary vane meanswhere said inlet discharges into said processing chamber so constructedand arranged as to impart a circulatory motion to the fluid mediumdischarged there.

1. In apparatus for separating solid particles entrained in a fluidmedia, comprising an elongated processing chamber having approximatelycylindrical side walls and having an inlet duct near one end for theintroduction of solid particles of varying sizes entrained in a fluidmedium and means for swirling the fluid media from said inlet duct, saidchamber having an outlet duct near its other end, said two ducts beingsubstantially coaxial and defining together a primary flow axis alongwhich said fluid medium travels from said inlet duct to said outletduct, agitating means for imparting to the primary flow of the medium insaid chamber a circulatory secondary flow causing said solid particlesto move through said chamber toward said inlet and adjacent said sidewalls, means forming a solid ground near the terminal end of said inletduct extending radially outwardly tHerefrom and terminating short ofsaid side walls and leaving there an annular open space through whichpass said solid particles moving toward said inlet end adjacent saidside walls, means providing a collection chamber for said solidparticles upstream of said inlet end beyond said solid ground, thearrangement being such as to form in said processing chamber a vortexsink near said solid ground and a vortex source remote from said inletduct toward said outlet duct; the combination therewith of means forclassifying as to size said solid particles passing through said openspace, comprising means for introducing into said processing chamber atthe inlet end thereof upstream of said primary flow from said solidground a fluid stream for classifying purposes, means for substantiallyeven dispersing said fluid stream about said annular space and directingthe fluid stream downstream through said space towards the outlet ducttogether with means for controlling the velocity of said classifyingstream, said side walls and said inlet and said solid ground confiningsaid classifying stream to said annular open space, whereby particles ofpredetermined smaller size only are driven counter current from saidsolid particles passing through said annular open space and the same arecarried through said processing chamber and through said outlet duct. 1.In apparatus for separating solid particles entrained in a fluid media,comprising an elongated processing chamber having approximatelycylindrical side walls and having an inlet duct near one end for theintroduction of solid particles of varying sizes entrained in a fluidmedium and means for swirling the fluid media from said inlet duct, saidchamber having an outlet duct near its other end, said two ducts beingsubstantially coaxial and defining together a primary flow axis alongwhich said fluid medium travels from said inlet duct to said outletduct, agitating means for imparting to the primary flow of the medium insaid chamber a circulatory secondary flow causing said solid particlesto move through said chamber toward said inlet and adjacent said sidewalls, means forming a solid ground near the terminal end of said inletduct extending radially outwardly tHerefrom and terminating short ofsaid side walls and leaving there an annular open space through whichpass said solid particles moving toward said inlet end adjacent saidside walls, means providing a collection chamber for said solidparticles upstream of said inlet end beyond said solid ground, thearrangement being such as to form in said processing chamber a vortexsink near said solid ground and a vortex source remote from said inletduct toward said outlet duct; the combination therewith of means forclassifying as to size said solid particles passing through said openspace, comprising means for introducing into said processing chamber atthe inlet end thereof upstream of said primary flow from said solidground a fluid stream for classifying purposes, means for substantiallyeven dispersing said fluid stream about said annular space and directingthe fluid stream downstream through said space towards the outlet ducttogether with means for controlling the velocity of said classifyingstream, said side walls and said inlet and said solid ground confiningsaid classifying stream to said annular open space, whereby particles ofpredetermined smaller size only are driven counter current from saidsolid particles passing through said annular open space and the same arecarried through said processing chamber and through said outlet duct. 2.Apparatus as defined in claim 1, wherein said processing chamber issubstantially vertical with said outlet duct uppermost.
 3. Apparatus asdefined in claim 1, wherein said agitating means comprises stationaryvane means where said inlet discharges into said processing chamber soconstructed and arranged as to impart a circulatory motion to the fluidmedium discharged there.
 4. Apparatus as defined in claim 1, whereinsaid fluid stream for classifying purposes is directed substantiallyradially with respect to said processing chamber.
 5. Apparatus asdefined in claim 1, wherein said fluid stream for classifying purposesis directed substantially tangentially with respect to said processingchamber.
 6. Apparatus as defined in claim 1, including vane means insaid processing chamber upstream from said solid ground so constructedand arranged as to direct said classifying fluid medium outwardly towardsaid side walls of said processing chamber.
 7. Apparatus as defined inclaim 1, wherein said solid particles introduced at said inlet duct areentrained in a gaseous medium, and said fluid stream for classifyingpurposes is gaseous.
 8. Apparatus as defined in claim 1, wherein saidagitating means comprises a plurality of fluid-injection nozzle meanscircumferentially spaced from each other about said axis, said nozzlemeans also being axially spaced from each other along said processingchamber, each of said nozzle means being directed substantiallytangentially to said side walls and inclined toward said inlet end.